Filament support for electric space discharge tubes



April 19, 1949. E. K. KELLEY I FILAMEN'I SUPPORT FOR ELECTRIC SPACE DISCHARGE TUBES Filed Oct. 29, 1945 Patented Apr. 19, 1949 FILAMEN T SUPPORT FOR ELECTRIC SPACE DISCHARGE TUBES Elton K. Kelley, Houston, Tex., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application October 29, 1945, Serial No. 625,147

8 Claims.

This invention relates to electric space discharge tubes of the vacuum type and more particularly to those of small sizes such as are used in pocket radios, hearing aid devices and the like.

In such tubes the problem of mounting the various tube elements on the usual insulating spacers presents various difficulties because of the small space available. Furthermore, where such tubes are likely to be subjected to great shock and vibration, the electrode elements must be secured in a manner to provide great rigidity.

It is among the objects of the present invention to provide a novel construction of the spacing elements ref-erred to and more particularly to provide for greater ease in the assembly of the cathod filaments and the securing thereof with greater rigidity.

The above and other objects of the invention will be fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 shows in side elevation, with parts in section, a discharge tube illustrating one embodiment of the invention;

Fig. 2 shows a section taken along line 2-2 of Fig. 1 and looking in the direction of the arrows;

Fig. 3 is a section taken along line 3--3 of Fig. 1 and looking in the direction of the arrows;

Fig. 4 shows a detail of one of the spacing insulators; and

Fig. 5 is a fragmentary section showing a modified form of the spacing insulator.

Referring to the drawing, reference numeral 6 indicates an envelope which in this instance is of glass of ellipsoidal form taken in a transverse section. With the envelope 6 is an electrode essembly comprising a pair of anode plates 1 having outwardly extending flanges 8 providing surfaces for the convenient welding of strips 9 thereto to unite the two anode plates in an integral structure. A lower spacing member ID, preferably of mica, supports the anode structure. An upper spacing member II also of insulating material, such as mica, rests upon the upper end of the anode structure. The two mica members In and II are rigidly secured together by tie rods I2 which project through the spacing members Ill and I l and are connected at their projecting ends by metal straps l3 providing stops serving to prevent relative motion between the anode structure and the spacing members I 0 and l l to thereby provide a unitary assembly which may be bodily inserted in the tube.

A pair of filamentary cathodes l4 extend centrally through the anode structure I and are surrounded by a grid I5, which is of elongated form taken in a transverse section, said grid being supported by grid side rods [6. U-bracket I1 is supported from the lower spacing member In and has welded thereto a pair of tabs 18, one for each of the filamentary cathodes [4. The tabs [8 are welded to the bracket I! at points which are out of alignment with an opening IS in the lower spacing member ID. The opening i9 through the member it] provides a pair of notches or corners 20 in the apexes of which the filamentary cathodes l4 are held. The apexes of the notches 20 are positioned on a line defined by the centers of the grid rods l6 so that the cathode filaments M will be held equally spaced from the grid wires IS. The upper spacing member H is provided with a V-shaped slot 2|. The apex of the slot 2i is positioned upon the center line of the tube and the two filamentary cathodes M are drawn together into the apex of the slot to form a V-shaped cathode. The upper ends of the filamentary cathodes H are provided with tabs 22 which are welded to the ends of conducting springs 23. Said ends of the conducting springs 23 are out of alignment with the apex of the V-slot 2| so that the filaments are drawn into the apex of the slot. The conducting springs 23 are wound on a cross bar 24 welded to a conducting side rod 25. The lower ends of the springs 23 are welded to one of the stops I 3 which stop is, in turn, welded to the side rod 25 and thus provides a bearing for the springs .23 as well as one of the holding stops for the upper insulating spacer II.

In order to secure greater rigidity of the side rod 25 relative to the remainder of the electrode assembly, tabs 21 are Welded at one end to the rod and bent over the upper and lower surfaces of the upper and lower spacers I0 and l i. A second side rod 28 similar to the rod 25 and positioned on the opposite side of the electrode assembly supports, at its upper end, a getter 29.

A lead-in conductor 3| secured to the projecting end of one of the rods I2 provides an external electrical connection to the anode 1. A lead-in conductor 32 secured to the U-bracket l1 provides one of the lead-in conductors for the filamentary cathode I4 and a similar lead-in conductor 33 attached to the lower end of the side rod 25 provides the other external connection for the cathode. A lead-in conductor 34 welded to the lower projecting end of one of the grid side- 3 rods I6 provides an external connection for the grid I5.

The electrode assembly described in the foregoing is inserted as a unit within a straight-sided glass tube forming the envelope 0. The lower end of this tube is heated and softened sufficiently so that it may be pressed to make the press or seal 35, hermetically sealing all of the external connections provided by the lead-in conductors 3|, 32, 33, and 34. For purposes of support an additional conductor 36 may be Welded to thelower end of side rod 28 and sealed in the press 35. This conductor may terminate in the press. The upper end of the tube is provided with the usual tubulation exhausted and sealed off at 31.

The construction described in the foregoing greatly facilitates the manufacture of the electrode assembly and increases the strength and rigidity thereof so that the tube may be made of very small dimensions and capable of withstanding great shock. For example, in the construction of one embodiment of the invention where the narrow inside dimension of the grid measures but 0.015 inch the filaments must be threaded through the openings in the upper and lower spacers with the end tabs i8 attached although the larger dimension of the tab is 0.020 of an inch. The openings l9 and H facilitate the insertion of the filaments and thereafter the vertex-es of the corners 20 and the apex of the V -slot 2| function to locate the two filament wires on the major transverse axis of the grid and Within the minor interior diameter thereof. Thus it becomes possible to pull the filaments into the locating corners and weld the tabs to the diagonal cross-bar simultaneously. The wires are thereafter prevented from slipping out of position since any movement of the wires along the side walls of the opening would require an increase in the length of the wire from the points of attachment at i8 to the opening. In other words, the distance from the points of attachment of the lower ends of the filaments at the tabs I8 to the vertexes 20 is less than the distance from these tabs to any other point along the adjacent side Walls of the opening. Similarly, the distance from the points of attachment of the upper ends of the filaments at the tabs .22 to the apex of the V-slot 2| is less than the distance from these tabs to any other point along the adjacent side walls of the slot.

It will be seen that the construction provides a V-formation for the filaments within the grid, both filaments being connected to the sam conductor at the bottom where they are held in accurately spaced relation, and converging together at the top.

Preferably, the opening l9 in the lower spacer art from a consideration of the forms shown and teachings hereof. Accordingly, a broad interpretation of the appended claims commensurate with the scope of the invention within the art is desired.

What is claimed is:

1. An elongated assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an anode structure, insulating spacers comprising an upper spacer and a lower spacer at the upper and lower ends of said anode structure, resilient members above the upper surface of said upper spacer, the upper ends of said filaments each being secured to one of said members, said lower spacer having an opening therein providing a pair of corners on opposite sides of the axis of said tube, said filaments passing through said opening, the ends of said filaments on the lower side of said lower spacer being secured at points out of alignment with said opening and beyond the edges thereof but respectively adjacent said corners, the filaments being drawn into the respective vertices of said corners by the tension of said resilient members.

2. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an anode structure, insulating spacers comprising an upper spacer and a lower spacer at the upper and lower ends of said anode structure, resilient members above the upper surface of said upper spacer, the upper ends of said filaments each being secured to one of said members, a V-slot in said upper spacer through which said filaments pass and into the apex of which they are drawn by said members, said lower spacer having an opening therein providing a pair of corners on opposite sides of the axis of said tube, said filaments passing through said opening, the ends of said filaments on the lower side of said lower spacer being secured at points out of alignment with said opening and beyond the edges thereof but respectively adjacent said corners, the filaments being drawn into the respective vertices of said corners by the tension of said resilient members.

3. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an anode structure, insulating spacers comprising an upper spacer and a lower spacer at the upper and lower ends of said anode structure, resilient members above the upper surface of said upper spacer, the upper ends of said filaments each being secured to one of said members, a V-slot in said upper spacer through which said filaments pass, said slot having its apex positioned on the axis of said tube, said filaments being drawn into said apex by said members, said lower spacer having an opening therein providing a pair of corners on opposite sides of the axis of said tube, said filaments passing through said opening, the ends of said filaments on the lower side of said lower spacer being secured at points out of alignment with said opening and beyond th edges thereof but respectively adjacent said corners, the filaments being drawn into the respective vertices of said corners by the tension of said resilient members.

4. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an anode structure, a grid of elongated transverse cross-section between said anode structure and said filaments, insulating spacers comprising an upper spacer and a lower spacer at the upper and lower ends of said anode structure, resilient members above the upper surface of said upper spacer, the upper ends of said filaments each being secured to one of said members, said lower spacer having an opening therein providing a pair of corners on opposite sides of the axis of said grid, each of said corners having its vertex on a line centered within the smaller transverse dimension of said grid, said filaments passing through said opening, the ends of said filaments on the lower side of said lower spacer being secured at points out of alignment with said opening and beyond the edges thereof but respectively adjacent said corners, the filaments being drawn into the respective vertices of said corners by the tension of said resilient members.

5. An electrode assembly for an electrical space discharge tube comprising a pair of filaments prOVidin-g a filamentary cathode, an additional electrode, spacing members comprising upper and lower insulating spacers, a bracket secured to the lower side of said lower spacer, said lower spacer having an opening therein, said opening having a pair of notches one for each of said filaments, said filaments being welded to said bracket at spaced points thereon which are out of alignment with said opening, beyond the edges thereof, and on opposite sides thereof, each of said filaments being drawn into the apex of one of said notches, a V-slot in said upper spacer, and tension means positioned above said upper spacer, said filaments being secured to said tension means at points out of alignment with said V-slot, beyond the edges thereof, and on the side adjacent the apex thereof, whereby said filaments are drawn together into said last-named apex.

6. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an additional electrode, spacing members comprising upper and lower insulating spacers, a bracket secured to the lower side of said lower spacer, said lower spacer having a central opening therein, said opening have a pair of notches on opposite sides of and in alignment with the center of said opening, said filaments being welded to said bracket at spaced points thereon which are out of alignment with said opening, beyond the edges thereof, and on opposite sides thereof, each of said filaments being drawn into the apex of one of said notches, V-slot in said upper spacer, and tension means positioned above said upper spacer, said filaments being secured to said tension means at points out of alignment with said V-slot, beyond the edges thereof, and on the side adjacent the apex thereof, whereby said filaments are drawn together into said last-named apex.

7. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a, filamentary cathode, an additional electrode, spacing members comprising upper and lower insulating spacers, a bracket secured to the lower side of said lower spacer, said lower spacer having a central opening therein, said opening having a pair of notches on opposite sides of and in alignment with the center of said opening, said filaments being welded to said bracket at spaced points thereon which are out of alignment with said opening, beyond the edges thereof, and on opposite sides thereof, each of said filaments being drawn into the apex of one of said notches, whereby said filaments are held apart at said lower spacer, and tension means positioned above said upper spacer, said filaments being drawn through an opening in said upper spacer and secured to said tension means at points out of alignment with and beyond the edges of. said last-mentioned opening.

8. An electrode assembly for an electrical space discharge tube comprising a pair of filaments providing a filamentary cathode, an additional electrode, spacing members comprising upper and lower insulating spacers, said lower spacer having an opening therethrough, said opening having a pair of notches, a common conductor on the lower side of said lower spacer, said filaments being welded to said common conductor at spaced points thereon which are out of alignment with said opening, beyond the edges thereof, and on opposite sides thereof, each of said filaments being dravm into the apex of one of said notches, said filaments extending through an opening in said upper spacer, and tension means positioned above said upper spacer, said filaments being secured to said tension means at points out of alignment with and beyond the edges of said lastmentioned opening but on the same side thereof, whereby said filaments are drawn together at said upper spacer.

ELTON K. KELLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,672,233 Skinner June 5, 1928 2,047,944 Ackman et a1 July 21, 1936 2,108,533 Henry Feb. 15, 1938 2,274,554 Krim Feb. 24, 1942 2,328,136 Gaebel Aug. 31, 1943 2,355,083 Krim Aug. 8, 1944 

